Biology subjects

Ghiran, I. C.

Publications and source records attributed to Ghiran, I. C..

3 recordsLinked to original sources

bioRxiv2026

Isoquercetin treatment of mouse sickled red blood cells shows a discernible deformability and sickling phenotype

IntroductionSickle cell disease is an inherited hemoglobinopathy with defective red cell deformability. The defective deformability promotes microvascular occlusion and subsequent vaso-occlusion in sickle cell disease patients. Previous studies have demonstrated that thiol isomerases, an endoplasmic reticulum-resident oxidoreductase that is released from vascular cells into the bloodstream, are present on red cell membrane and contribute to cellular dehydration and sickling. However, the role of membrane-bound thiol isomerases on sickled red blood cells is unclear. MethodsUsing red blood cells from Townes humanized sickle cell or non-sickled mice, we performed ektacytometry assay under shear using laser assisted optical rotational cell analyzer (LORRCA) to assess the effects of antagonizing thiol isomerases with isoquercetin and a functional blocking monoclonal antibody. The densitometric properties of sickled red blood cells in the presence of isoquercetin was also tested using magnetic levitation. ResultsThiol isomerase antagonism increased sickled red cell elongation, cellular dehydration and the diamagnetic signature compared to control treatment. ConclusionThiol isomerases may be involved in regulating sickled red blood cells mechanical properties through mechanisms that require further investigation.

pharmacology and toxicology↗

bioRxiv2019

Rational Design of a Bifunctional AND-Gate Ligand to Modulate Cell-Cell Interactions

Protein \"AND-gate\" systems, in which a ligand acts only on cells with two different receptors, direct signaling activity to a particular cell type and avoid action on other cells. In a bifunctional AND-Gate protein, the molecular geometry of the protein domains is crucial. Here we constructed a tissue-targeted erythropoietin (EPO) that stimulates red blood cell (RBC) production without triggering thrombosis. EPO was directed to RBC precursors and mature RBCs by fusion to an anti-glycophorin A antibody V region. Many such constructs activated EPO receptors in vitro and stimulated RBC and not platelet production in mice but nonetheless enhanced thrombosis in mice and caused adhesion between RBCs and EPO receptor-bearing cells. Based on a protein-structural model of the RBC surface, we rationally designed an anti-glycophorin/EPO fusion that does not induce cell adhesion in vitro or enhance thrombosis in vivo. Thus, meso-scale geometry can inform design of synthetic-biological systems.\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC=\"FIGDIR/small/711549v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (22K):\norg.highwire.dtl.DTLVardef@93b382org.highwire.dtl.DTLVardef@ee37ccorg.highwire.dtl.DTLVardef@1913fe4org.highwire.dtl.DTLVardef@f998b1_HPS_FORMAT_FIGEXP M_FIG C_FIG

synthetic biology↗

bioRxiv2017

Myosin IIA interacts with the spectrin-actin membrane skeleton to control red blood cell membrane curvature and deformability

The biconcave disc shape and deformability of mammalian red blood cells (RBCs) relies upon the membrane skeleton, a viscoelastic network of short, membrane-associated actin filaments (F-actin) cross-linked by long, flexible spectrin tetramers. Nonmuscle myosin II (NMII) motors exert force on diverse F-actin networks to control cell shapes, but a function for NMII contractility in the 2D spectrin-F-actin network in RBCs has not been tested. Here, we show that RBCs contain membrane skeleton-associated NMIIA puncta, identified as bipolar filaments by super-resolution fluorescence microscopy. NMIIA association with the membrane skeleton is ATP-dependent, consistent with NMIIA motor domains binding to membrane skeleton F-actin and contributing to membrane mechanical stability. In addition, the NMIIA heavy and light chains are phosphorylated in vivo in RBCs, indicating active regulation of NMIIA motor activity and filament assembly, while reduced heavy chain phosphorylation of membrane skeleton-associated NMIIA indicates assembly of stable filaments at the membrane. Treatment of RBCs with blebbistatin, an inhibitor of NMII motor activity, decreases the number of NMIIA filaments associated with the membrane and enhances local, nanoscale membrane oscillations, suggesting decreased membrane tension. Blebbistatin-treated RBCs also exhibit elongated shapes, loss of membrane curvature, and enhanced deformability, indicating a role for NMIIA contractility in promoting membrane stiffness and maintaining RBC biconcave disc cell shape. As structures similar to the RBC membrane skeleton are conserved in many metazoan cell types, these data demonstrate a general function for NMII in controlling specialized membrane morphology and mechanical properties through contractile interactions with short F-actin in spectrin-F-actin networks.\n\nSignificance statementThe biconcave disc shape and deformability of the mammalian RBC is vital to its circulatory function, relying upon a 2D viscoelastic spectrin-F-actin network attached to the membrane. A role for myosin II (NMII) contractility in generating tension in this network and controlling RBC shape has never been tested. We show that NMIIA forms phosphorylated bipolar filaments in RBCs, which associate with F-actin at the membrane. NMIIA motor activity is required for interactions with the spectrin-F-actin network, and regulates RBC biconcave shape and deformability. These results provide a novel mechanism for actomyosin force generation at the plasma membrane, and may be applicable to other cell types such as neurons and polarized epithelial cells with a spectrin-F-actin-based membrane skeleton.

cell biology↗